Heat oil in a large pan, then saute vegetables for 5 minutes.
Cover with water (about 1.5l), add bouquet garni and onion.
Bring to the boil and leave to cook for 30 minutes.
Add prunes.
Season, then leave to simmer for 15 minutes.
Sprinkle with nutmeg.
Put a few croutons in the bottom of each soup dish, then pour in soup.
Sprinkle with parsley and serve